No one has been arrested for the crash, which occurred while Ukrainians were fighting Russian-backed separatists. Ukrainian officials blamed the Russians for the crash.

In a letter to Trump Friday, the relatives said they made the request because Trump and Russian President Vladimir Putin are set to meet later this month at a peace summit in Argentina. They said Trump's tough stance in the case of slain Saudi journalist Jamal Khashoggi gives them hope he will get to the bottom of what happened to MH17.

"As long as we can also agree on the fact that the enduring cover-up for 298 murders on all MH-17 passengers and crew, is in the same category," the group wrote in the letter. "No responsibility has been taken by anyone. Instead, several obvious attempts have been made to cover-up what really happened on that horrific summer's day."

PRESS RELEASE - MH-17 Victims' families confront both Trump and Putin

Families of victims of Flight MH17 have recently written President Trump. Working group Truth finding MH17 is asking for Trump's help, following news that he will meet with President Putin later this month. pic.twitter.com/6h8POx0GUt

Family members -- including American Thomas Schansman, whose son was the lone American killed on the flight -- said they believe Putin has the answers.

"Although we still cannot know what the exact Russian Federation's role was, they have floated multiple versions of what must have happened -- versions that have all be refuted by the facts we do know, as well as evidence," the letter said. "We understand that confidential intelligence available to your government also fully sustains this notion."